The present invention relates to microlithography and more particularly to a unitary flexure stage permitting essentially lossless small angle relative rotation.
In the manufacture of semiconductor integrated circuits, circuit features are formed by making successive microlithographic exposures on resists coated on the surface of a semiconductor wafer. As is understood, it is essential to the manufacturing process that successive exposures be precisely aligned with each other. To achieve this alignment, it is necessary to provide both translational and rotational freedom of movement of the wafer relative to the projected image. The projected image is typically determined by a reticle held in a step and repeat microlithographic projector. In order to permit a servo system to accurately position the wafer for the last or fine adjustment process, it is important that freedom of movement be provided by means of a system of mounting or support which does not introduce loss or mechanical hysteresis and which does not introduce spurious or unstable forces which would disrupt the accuracy of the servo system.
The present invention is particularly concerned with the provision of a stage which permits essentially lossless small angle relative rotation of a central portion of a stage with respect to an outer or annular portion.
Among the several objects of the present invention may be noted the provision of a stage permitting essentially lossless small angle relative rotation; the provision of such a stage which does not introduce unstable or reversing forces; the provision of such a stage which does not exhibit hystersis; the provision of such a stage which facilitates highly accurate positioning; the provision of such a stage which is highly reliable and which is of relatively simple and inexpensive construction. Other objects and features will be in part apparent and in part pointed out hereinafter.